A conductor of a telephone cord which connects a telephone handset to a telephone base and a telephone base to a wall terminal generally comprises a polymeric core having a plurality of tinsel ribbons wrapped helically thereabout. The tinsel conductors are covered with a suitable insulative covering such as that, for example, which is disclosed and claimed in U.S. Pat. No. 4,090,763 issued on May 23, 1978 in the names of W. I. Congdon et al. A plurality of the individual insulated conductors are jacketed with a plasticized polyvinyl chloride (PVC) composition.
In a commonly used cord connection arrangement, each end of a line or handset cord is terminated with a miniature plug, which is termed modular, to facilitate attachment to jacks in telephone instruments and in wall outlets. An end of a cord is inserted into one of a modular plug and secured therein. The modular plug is adapted to be inserted into a cavity of a jack to establish electrical connections between cord conductors which are terminated within the plug and contact elements in the form of wires in the jack. Modular plugs are disclosed, for example, in U.S. Pat. Nos. 3,699,498 and 4,148,539 which issued Oct. 17,1972 and Apr. 10, 1979, respectively, in the names of E. C. Hardesty, C. L. Krumreich, A. E. Mulbarger, Jr., and S. W. Walden and in the name of E. C. Hardesty.
Typically, a modular plug includes a plastic housing having conductor-receiving troughs which communicate with a cord-receiving opening at one end of the plug. An opposite end of the plug is referred to as a termination or free end. Terminal-receiving slots extend between the troughs and an outwardly facing inner surface of a well of the housing from which a plurality of partitions extend to an outer surface of the housing. Each slot opens to the inner surface of the well between two partitions or between a partition and a sidewall of the housing.
In the termination of a cord with a plug, the jacket is removed from an end portion of a length of cordage. That end portion is inserted into the cord-receiving end of the plug with end portions of the conductors being received in the plug troughs. Then the end portion of the length of cordage is secured within the plug and the plug is positioned in a nest to receive a plurality of terminals. Plated strips of terminal are fed into insertion apparatus such as is shown in U.S. Pat. No. 3,839,787 which issued on Oct. 8,1974 in the names of W. B. Brown and F. D. Gavin. Terminals are severed from the strips and seated within the terminal receiving slots to engage electrically the cord conductors in the troughs. The slots are spaced to cause the seated terminals to engage the contact wires when the plug is inserted into a jack cavity and thereby connect electrically the cord conductors to the jact.
One prior terminal is described in abovementioned U.S. Pat. No. 4,184,539. It is made from sheet stock of an electrically conductive material such as, for example, a Phosphor-bronze alloy. The terminal has flat faces spaced apart by an edge surface which includes an internal contact portion comprising protruding tangs. When the terminals are seated fully within the plug housing, the tangs pierce the insulation of and engage electrically the conductors of the cord which has been inserted into the one end of the plug.
Each terminal also includes an external contact portion being exposed to an outer surface of the housing and having an outer surface which is spaced slightly from outer edge surfaces of the partitions which are coplanar with the outer surface of the housing. These portions of the terminals are adapted to complete electrical connections from the conductors of the cord to the jack. Each external contact portion includes and edge surface having a crown of a predetermined radius formed at each end thereof. The terminal is symmetrical with respect to an axis which extends through its center of gravity and which is normal to the edge surface of the external contact portion.
That crown which is adjacent to the termination end of the plug housing functions to engage an aligned wire-like contact element of the jack into which the plug is inserted. Inasmuch as the wire-like contact element of the jack extends angularly within the cavity of the jack into which the plug is inserted, the contact element engages only a portion of the aligned terminal, specifically a portion of the crown adjacent to the termination end of the plug.
Substantially the entire surface area of the hereinbefore-described terminal is covered with a layer or layers of metallic material by a process such as electroplating, for example. Only those edge surfaces of the terminals which are formed as each terminal is severed from its strip are unplated. Substantially the entire surface area is covered with nickel which provides corrosion resistance, smooths the terminal metal, and prevents diffusion of the terminal metal into a subsequently deposited layer of metallic material. The nickel is covered with a relatively thin layer of gold which is called a strike and which enhances the connection of the cord conductor.
Also, selected surface areas of the external contact point have been covered with an additional layer of metallic material such as gold to enhance the conductivity of the connection with a contact wire of the jack. The selected portions include the crowns because they are exposed and because one of the crowns of each terminal is engaged by an aligned contact wire of a jack. The exposed edge surface between the crowns also is covered, as well as a relatively small portion of each flat side surface.
Significant cost savings have been realized by reducing the area of the selected surface portions which are covered, particularly in view of the large number of plugs which are manufactured each year. The foregoing problem has been overcome by a relatively new flat blade-like terminal in which the external contact portion of the blade has been reconfigured to resemble a fin, for example. Each terminal is made of an electrically conductive material and comprises a body portion which includes a reference surface that extends from a first end of the terminal toward a second end. The terminal includes an internal contact portion for piercing the insulation of and making an electrical connection with a cord conductor when the terminal is seated fully in the plug housing. Each terminal also includes a fin-like portion having a curved leading edge surface which is adjacent to the termination end of the plug housing and a linear trailing edge surface that is normal to the reference edge surface. Inasmuch as the curved edge surface only is engaged by the wire-like contact element of a jack when the plug is inserted into its cavity, only it and portions of adjoining side surfaces are plated with the gold. The external contact portion protrudes from the body portion and is disposed asymmetrically between the ends of the body portion adjacent to the first end of the terminal.
A terminal having the reconfigured external contact portion is inserted into each slot of the housing such that the first end and hence the external contact portion of each is oriented toward the termination end of the housing. The internal contact portion of the terminal establishes an electrical connection with a conductor of the cord that has been inserted into the housing prior to the insertion of the terminals. The external contact portion of each terminal extends beyond the slot in which the terminal is seated and is adapted to make electrical engagement with a wire-like contact element of a jack when the plug is inserted into the cavity of the jack.
In a method of assembling the terminal having the reconfigured external contact portions with a plug housing, rams which are used to insert the terminals in the housing do not engage the selected portions of the surface area which have been plated with the gold, but instead engage the reference surface between the trailing edge of the external contact portion and the trailing edge of the terminal. This avoids inadvertent removal of the selective plating. Also, the external contact portion which is positioned along the body portion is offset sufficiently from a centerline of the terminal to allow a ram to insert the terminal in the plug housing without canting it.
It is not uncommon that after a period of use, cords are refurbished by service organizations, which generally do not have the capital investment in equipment found in a manufacturing environment. When cords are refurbished, it is desired to reterminate one or both ends of the cords with modular plugs. Furthermore, it is not uncommon in today's world for a customer to terminate cordage with a modular plug.
Desirably, modular plugs which have been factory assembled to the point of having the terminals thereof partially inserted are available commercially. The service organizations and/or customers then need only insert the cord, actuate strain relief facilities such as are shown in U.S. Pat. No. 4,148,539 and seat completely the terminals.
Each terminal has barbs formed on opposed end surfaces thereof. The barbs and the lengths of the slots in the housing are such that they cooperate to support the terminals within the openings to space the external contact portions above the inner surface of the well with the barbs being embedded in end walls which define the slots to prevent unintended pivotal movement of the terminals while each of the terminals is in a partially inserted position. Upon the further application of insertion forces to the terminals subsequent to insertion of conductors into the cavity, the terminals are caused to be moved further into the slots to embed another set of barbs in the material defining the slot and seat fully the terminals within the housing. The embedding of the barbs in the material defining the slots stabilizes the terminal and prevents unintended lateral and longitudinal as well as linear movements thereof.
In order to seat the terminals in the modular plug, a tool having a plurality of spaced blade-like rams is moved to engage exposed portions of the terminals. Each ram engages an exposed edge surface of a terminal and as the tool is moved toward the plug, each ram is received between two partition walls or between a partition wall and a sidewall of the housing. Such tools are expensive because of the precision required to be able to move the blade-like ram portions between partition walls or partition walls and sidewalls of the housing. Also, the relatively thin rams may slip to one side of the terminals. Further, care must be taken to insure that the ram which follows the associated terminal inserts the terminal into its slot so that a predetermined portion of the terminal protrudes above the inner surface of the well toward the outer surface of the housing. This distance by which the terminal protrudes from its slot is an F.C.C. requirement. These problems are exacerbated when hand tools are used by customers to seat the terminals to terminate a cord.
What is needed and seemingly what is not shown in the prior art is a modular plug which includes a housing that facilitates the insertion of a plurality of terminals to a predetermined depth within the housing. It should be apparent that a modular plug which is a solution to this problem is one that has the same outer configuration as the presently manufactured plugs and which will be matable with presently used modular jacks.